1. Field of the Invention
The present invention relates to a novel compound, to processes for preparing it and to its use in treating medical disorders. In particular the present invention relates to a novel derivative of Amlodipine.
2. Description of the Related Arts
Calcium channel blockers (calcium antagonists) are useful in treating cardiac conditions including angina and/or hypertension. Dicarboxylate-dihydropyridine derivatives are generally known to possess calcium channel blocking activity. For example, EP 089 167 and corresponding U.S. Pat. No. 4,572,909 disclose a class of 2-amino group, 3,5-dicarboxylate dihydropyridine derivatives as being useful calcium channel blockers. These patents identify that one of the most preferred compounds is 2-[(2-aminoethoxy)methyl]-4-(2-chlorophenyl)-3-ethoxycarbonyl-5-methoxycarbonyl-6-methyl-1,4-dihydropyridine. This compound, which is now commonly known as amlodipine, has the following formula: 
Amlodipine exhibits good bioavailability and has a long half-life in the body. While a variety of acid addition salts are taught in these patents to be suitable, the maleate salt is identified as the most preferred acid addition salt. However, the commercial product of amlodipine (NORVASC by Pfizer) uses amlodipine besylate (benzene sulfonate) and not amlodipine maleate. Indeed, subsequent patents EP 244 944 and corresponding U.S. Pat. No. 4,879,303 indicate that the besylate salt provides certain advantages over the known salts including good formulating properties. Apparently, amlodipine maleate suffered from tabletting and stability problems so as to cause a switch during development to the besylate salt. (See xe2x80x9cReview of Original NDAxe2x80x9d for NDA# 19-787 of 10.10.1990, obtainable from FDA under Freedom of Information Act). The stability and tabletting issues/causes are not publicly disclosed in the information available from the FDA.
The present invention relates to the discovery of a novel derivative of amlodipine, the use thereof, and methods of making the same. Specifically, the present invention provides a compound of the following formula (1): 
or a pharmaceutically acceptable salt thereof.
The compound of formula (1) is useful as a calcium channel blocker and thus further aspects of the invention relate to a pharmaceutical composition comprising an effective amount of a compound of formula (1) or a pharmaceutically acceptable salt thereof and a pharmaceutically acceptable excipient as well as a method of treating angina or hypertension by administering to a patient in need thereof an effective amount of a compound of formula (1) or a pharmaceutically acceptable salt thereof. Further, the present invention can be used in combination with amlodipine as a pharmaceutically active ingredient composition. The compound of formula (1) can be made by a process that comprises reacting amlodipine or a salt thereof with a carbonyl-activated maleic acid compound.